Environmental Art

Bone black is blue-black in color and fairly smooth in texture and also denser than lamp black. It contains about 10% carbon, 84% calcium phosphate and 6 % calcium carbonate. It is made from charring of bones or waste ivory. It was used from prehistory and it is in use until today. Ivory Black is therefore the least pure form of carbon black, containing a high percentage of calcium phosphate.

Bone black is prepared by charring bones, horns etc. in the absence of air. It is the deepest black but it was not used as widely as charcoal black. Fragments or turnings of ivory, or of the osseous parts of animals are put into a crucible surrounded by burning coals and covered. The ivory or bones, by exposure to the heat, were reduced to charcoal.

Charred bones itself has also found its use in many applications outside of just pigments. One interesting example, is its use in decolorizing sugar, as well as wine and vinegar. Charred bones, used to make the deepest of blacks, is also the reason for the pure white sugar bought from store shelves.

Chemical name: calcium phosphate + calcium carbonate +carbon
Formula:
Ca3(PO4)2 + CaCO3 +C

Color Index (C.I.)

PBk 9

Left to Right | Wild Clay vessel with pigment and earth sealed with milk glaze and fired in the fireplace, Wild Clay vessel with pigments and earth fired in fireplace, Wild Clay vessel with pigments and earth awaiting it’s time in the embers.

I have begun to experiment with some 11,700 year old wild clay that I sustainably harvested along the banks of the shallows of the Hudson River. Crusted with slip, iron oxide pigments and Earth from Schoharie NY – they were first fired in my fireplace transforming their structure and color. To seal and protect them from the elements, they were then sealed with a thin coating of Cow’s milk and heated on high in the oven – the colors deepening as it warmed, the house smelling of caramel sweetness.

This wild clay is a bit tricky to work with – as you wet it to shape it, it wishes to slip between your fingers, becoming more fluid, defiantly refusing to maintain it’s man made form – it was a lovely lesson in balance. That we humans should not always force our will upon this land and it’s gifts. When I allowed the clay to take it’s shape organically, when I worked together with it to find that compromise – to allow it to be, while gently working with it in transformation – it all came together and took form. However, not in the way that I initially intended, but in a way that was even more beautiful, that changed my relationship, perception and intent of it. I was able to create something I could use in harmony with the Earth and it’s gift – though the lesson the Earth taught me during this project – may have been the more precious gift after all.